Nutating antenna



B. J. FISHER, JR

NUTATING ANTENNA July 21, 1953 Filed Oct. 26, 1945 Sm. m QNLQN @am vw Invebor". Benjamin J. Fisher; Jr:

His Attorney..

Patented July 21, 1953 rNU'r'A'rING. ANTENA l Benjamin J. Fisher, Jr., Utica, N. Y., assigner to General Electric Company, a'corporation of New York Application octber ze, 1945, serial No. 624,779

My'invention relates to radio detection and ranging systems and it has for its primary object to provide a new and improved antenna for such a system.

In radio detection and ranging system in which high frequency signals are radiated from an antenna and are received after reflection from van object in the path of the signals, it has been olb-l served that greater-directivity of the radiated beam is obtained if a short conical beam is employed of the type which may be obtained when the signals radiated are of such a high frequency that wave guide systems are employed for transmitting these signals to the antenna. It has been further observed that the greatest amount of energy is reflectedV from an object in the path of the signals if the high frequency wave radiated from the antenna has a particular polarization characteristic and .if this characteristic is maintained constant as the radiating element is rotated about the axis of a reflector to provide a conical beam, the apex angle of the cone of radiation being as small yas possible. Accordingly, it is an object of my invention to provide a new and improved antenna for a system of this type in which the radiating element is nutated about the axis of a reflector.

It is a still-further object of my invention to provide a new and improved nutating antenna which is diametrically balanced. y Y

It is still another object of my invention to pro,- vide a new and improved nutating antenna employing a wave guide having a flexible joint so that it may be easily connected to an associatedwave guide system.

One of the features of my invention consists in the use in'a nutating antenna of a Wave guide which is inclined at an angle to the axis of the reflector, one point onV the wave guide vbeingfixed with respect to the axis of the reiiector and eccentric means being provided at another point of the wave guide to move the end of the guide in a circular path without rotation about its own axis.

The features of my invention which I believe to be novel are set forth with particularity inthe appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects. and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing, in which Fig. 1 is a vertical sectional view of an antenna embodying my invention, and Fig. 2 is an end view ofthe radiating element of theantenna of c Claims. (c1. 25o-33.65)

Referring to Figs. 1 and 2 jointly, there is shown an antenna suitable for use in a radio detection and ranging system and which comprises a parabolic reflector element i anda section of rectangular wave guide 2 which is inclined at an angle to the axis of the reector I and whichv has one of its ends connected to a stationary wave guide 3, which may be connected to any suitable source ofhigh frequency signals and which, on its other end, carries 'a radiating element 4. The reflector I may comprise a suitablev metallic memberv which is parabolic in cross-section and which may be either solid or perforated, as desired. The wave guide 2 is ofthe hollow pipe type. rectangular in cross-section and formed g of a suitable metal, such asvcopper or brass. The radiating element 4 comprisesa metallic diskshaped plate or baffle 5 which is spacedoutwardly from the lopen end of the waveguide 2 and a metallic flange member 6' which surrounds the wave guide 2 at 'its open end and supports the baffle member 5. As may be seen in Fig. 2, the flange member 6 is provided with a pair of parallel slots 1, 8 spaced from the wave guide 2 and lying-parallel to the larger dimension of the wave guide 2. The slots 1, 8 are so positioned with respect to theV wave guide 2 and the'baiile plate 5 kthat high frequency energy transmitted along the wave guide 2 isreflected by the baille 5V through the slots 1 and 8 and directed substantially parallel with the outer surface of the wave. Y

guide.

g The reflector I is supported from Va circular housing 9 by any suitable means, such as the screws I0, the reflector I substantially closing one end of the housing 9. The opposite endV of the housing 9 is closed by an end plate II which supports the endof the stationary wave guide 3. Disposed between the end plate I I and the housing 9 is a stationary bearing member I2 having a spherical bearing surface I3. A tubular sleeve member I4, which surrounds the wave guide 2 near its left-hand end, has a spherical ball surface I5 which is journalled in the surface I3. Means are provided. forpreventing 'rotation of the sleeve I4 in the sphericalv surface I3 and comprise the pin I6 located in the bearing member I2 and extending into a longitudinal slot. I1

in the sleeve I4.

At its opposite end, the sleeve I4 is supported by a ball bearing construction having an inner race member I8 affixed to the sleeve I4 and a second or outer race member I9 supported in a cup-shaped end 20 of a hollow shaft 2I. Lock nuts 22, 23 are provided, respectively,vto secure the races I8Y and I9 to-the'members Iliana 20.

The hollow shaft 2l, in turn, is rotatably supported by a pair of ball bearings 24, 25 having outer races secured to the housing member 9. The outer surface of the hollow shaft 2| is likewise provided with Va gear 25 which engages a suitable driving pinion 21.

In order thatthe wave guide 2 nutate about the axis of the reflector l as the hollow shaft 2| is rotated by the gears 26, 21, the cup-shaped end 20 is bored eccentrically with respect to the main portion of the shaft 2 I. This is illustrated in the drawing by the wall portion 281 on the cup end 2li which is shown to be larger than the opposite wall portion 29. Preferably, theV ball bearing structure i8, I 9 is of the self-aligning'type so that, as the shaft 2l rotates, the radiating element 4 at the end of the wave guide moves in av circular path about the axis of the reflectorl l. At the same time, the pin i6 provides a fixed point at the pivot end of the wave guide 2 so that the waveguide nutates about the axis of the reflector without rotating about its ownaxis.

Meansare provided-for conducting high frequency energy from the wave guide 3 to the Wave guide 2 without loss at the pivoted end and comprise a half wave choke 3i) formed by a longitudinal slot in the fixed end of the sleeve i4. Likewise, means are provided for preventing moisture from entering the housing 9 through the opening 3l in the reflector l and comprise a flexible gasket 32 which is clamped at its inner edge between a flange 33, secured to the louter surface of the'wave guide 2, and a ring 34 and, at its ara/ratos outer edge,be`tween the inwardly directed flange 355 within the housing 9 and a ring 3E. 34, 36 may be secured to the flanges 33, 35 in any suitable manner, such as by screws, not shown.

In order that the nutating antenna be dynamically balanced as the shaft 2l is rotated by means of the gears 2E, 21 to nutate wave guide 2, a pair o-f balance weights 31, 38 are provided, the weight 31 being attached to the hollow shaft 2l by a screw 39 between the pivoted end of the wave guide and the gear 26, and the weight 38 being attached by a screw near the open end of the cup-shaped end 20.

In ,the operation of the antenna described, as the hollow shaft 2l is rotated by means ofgears 2B, 21, the bearing structure I8, I9 supported within the cup-shaped end 2U of the shaft carries the sleeve i4 in a circular path about the axis of the shaft 2l. The pin IB, at the same time, prevents rotation of the fixed end of the sleeve I4 in the bearing surface i3. The high frequency waves transmitted over the wave guides 3 and 2, therefore, are reflected from the balile plate 5 and pass through the opening 1, 8 in the flange 6 to describe a conical beam of radiation about the axis of the reflector l.

A11 important advantage of the nutating antenna described is that it permits the useof a rectangular wave guide for transmitting high fre, quency Waves, so that waves of a desired polarization may be radiated by the antenna. It has been found in certain applications, for example when high frequency waves are radiated over a body of water, that waves having a particular:

The rings polarization are especially suited for use in radio guide system is that it permits the use of highery frequency wavesin generating a. conical beam 4 f of radiation by employing a rectangular wave guide with its desirable energy transmission and polarization characteristics.

While the invention has been described by reference to a particular embodiment thereof, it will be understood that numerous modifications may be made -by those skilled in the art without departing from the invention. I therefore aim in the appended claims to cover all such equivalent variations as come Within the true spirit andI scope of my invention.

Letters Patent of the United States, is:

1. In an antenna of the type having a stationary reector having an axis, a section of wave guide extending through said reflector, and means for nutating said section about said axis comprising, means for maintaining one end of said guide substantially stationary with respect to said axis, means for preventing rotation of said one end about said axis, means eccentric to s-aid axis surrounding said guide at a point spaced from said one end, means for rotating said last means, and rotatable means supporting said guide within said eccentric means.

` 2. In an antenna of the type having a station'- ary relector having an axis, a section of wave guide extending 'through said reflector, means for maintaining arst point of said guide substantially stationary with respect to said axis, said point being spaced from said reflector, meansy for preventing rotation of said first point of said `guide about said axis, a rotating sleeve surrounding said guide between said point and said reflector, and eccentrica-ily rotatable means disposed between said sleeve and said guide whereby the portions of said guide spaced from said point are nutated about said axis.

3. In an antenna of the type having a stationary reector having an axis, a section of waveguide extending through said reflector, means for maintaining a point of said guide spaced from said reflector substantially stationary with respect to said axis, means for preventing rotation of said point of said guide about said axis, a rotatable sleeve member surrounding said guide between said point and said reflector, said sleeve being rotatable about said axis, said sleeve having a portion eccentri-c to said axis, and means journalling said guide in said portion, whereby as said sleeve is rotated said guide is nutated abou said axis; 4. In an antenna of the type having a stationary reflector having an axis, a section of wave guide extending through said reector, a housing member supported from said reflector, means within said housing member for maintaining a point of said guide substantially stationary with respect to said axis, means for preventing rotation of said point of said guide about said axis, a rotatable sleeve Amember within said housing and surrounding said guide, said sleeve being rotatable about said axis, said sleeve having a portion eccentric to said axis, and means journalling said guide in said portion, Whereby'as said sleeve'is rotated said guide is nutated about said axis.

5. A nutating antenna comprising a stationary reflector having an axis, a wave guide inclined at a small angle to said axis and having a portion extending in front of said reflector, said guide having one end substantially xed with respect to said axis, means for preventing rotatoin of said one end about said axis, and means for nu'- tating the other end of said guide about said axis comprising a rotatable sleeve surrounding.

said guide, said sleeve having an eccentric vportion rotatably supporting said guide.

6. An antenna comprising a stationary reflector having an axis, a rectangular Wave guide extending through said reector, said guide being oriented to transmit Waves of a desired polarization, said guide having one end substantially xed with respect to said axis, means for preventing rotation of said one end about said axis, and means for nutating theother end of said guide about said axis, whereby said orientation is maintained and waves of said polarization may be transmitted throughv said guide substantially Without reection therein as said other end is nutated about said axis.

BENJAIVIIN J. FISHER, VJ R.

Number 5 1,085,867 1,548,948 1,918,358 2,188,938 2,206,923 10 2,365,048 2,412,867 2,415,103 2,457,562

15, Number 450,484

Name Date Kennedy Feb. 3, 1914 Sperry Aug. 11, 1925 Walton July 18, 1933 Brown et al Feb. `6, 1940 'Southworth July 9, 1940 Bruno Dec. 12, 1944 Briggs et al. Dec. 17, 1946 Langstroth Feb., 4, 1947 Karleen Dec. 28, 1948 FOREIGN PATENTS Country Date Great Britain Ju1y 2o, 193e 

